Command Line Tips and Hacks

Command line tricks, tools, tips and hacks to help you get the most out of the shell prompt in Linux, *BSD, Apple OS X and Unix like operating systems ( rss feed ) .

If you want to monitor network throughput on the command line interface, use nload application. It is a console application which monitors network traffic and bandwidth usage in real time. It visualizes the in and outgoing traffic using two graphs and provides additional info like total amount of transferred data and min/max network usage.

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Linux and Unix are multitasking operating systems i.e. a system that can run multiple tasks (process) during the same period of time. In this new blog series, I am going to list the Linux and Unix job control commands that you can use for multitasking with the Bash or Korn or POSIX shell.

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You can dump Linux or Unix server memory. This is useful for forensics analysis, and testing your own system. This is often desirable to see:

  • What code and what data actually resides in memory.
  • You can search for specific pids memory.
  • Search memory for string and other data such as passwords.
  • Works as add-on tool for gdb and others.
  • Search/replace/dump memory from running processes and core files.
  • All kinds of deep hacking activities that simply saves your time and solve problems.

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nicstat-welcomeThe nicstat command is top like utility for network interface card (NIC). It displays information and statistics about all your network card such as packets, kilobytes per second, average packet sizes and more. It works under Solaris and Linux operating systems.

In this post, I will explain how to install and use the nicstat command to find out stats about your NICs under Debian / Ubuntu / RHEL / CentOS Linux operating systems.

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Linux on the desktop is making great progress. However, the real beauty of Linux and Unix like operating system lies beneath the surface at the command prompt. nixCraft picks his best open source terminal applications of 2012.

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Nmap is short for Network Mapper. It is an open source security tool for network exploration, security scanning and auditing. However, nmap command comes with lots of options that can make the utility more robust and difficult to follow for new users.

The purpose of this post is to introduce a user to the nmap command line tool to scan a host and/or network, so to find out the possible vulnerable points in the hosts. You will also learn how to use Nmap for offensive and defensive purposes.

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The diff command compare files line by line and displays a list of changes between two file. You can use diff command to:

  1. See the changes between one version of a file.
  2. Compare two configuration or program files.
  3. Create a patch file which can be applied with the Linux / Unix program patch.

Say hello to colordiff

colordiff is a wrapper for diff and produces the same output as diff but with coloured syntax highlighting at the command line to improve readability. colordiff has been tested on various flavours of Linux and under OpenBSD, but should be broadly portable to other systems.

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The HTTP 2xx class of status codes indicates the action requested by the client was received, and processed successfully. HTTP/1.1 200 OK is the standard response for successful HTTP requests. When you type www.cyberciti.biz in the browser you will get this status code. The HTTP/1.1 206 status code allows the client to grab only part of the resource by sending a range header. This is useful for:

  1. Understanding http headers and protocol.
  2. Troubleshooting network problems.
  3. Troubleshooting large download problems.
  4. Troubleshooting CDN and origin HTTP server problems.
  5. Test resuming interrupted downloads using tools like lftp or wget or telnet.
  6. Test and split a large file size into multiple simultaneous streams i.e. download a large file in parts.

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Reading an IP address in a shell script requires many time and various Linux distributions stores IP address in different text files. So most of us end up writing shell pipes/scripts to get the information using ifconfig | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}' syntax. There is an alternative to ifconfig+shell pipe hack – ifdata command. It is a little know tool that can be used to check for the existence of a network interface and find out info about your interface such as IP, netmask, MTU and much more. No need to write shell pipes and fetch information via ifconfig or ip command. This command is designed to be easily used by a shell script.

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Most sysadmin will run low on disk space. Users will demand more space and you need to free space. You will find out files that’s a waste of space and delete it or move to an archive medium. But, how do you find the right files to delete that can help recover maximum space? Say hello to agedu tool (pronounced as ‘age dee you’) – it scans a directory tree and produces reports about how much disk space is used in each directory and subdirectory, and also how that usage of disk space corresponds to files with last-access times a long time ago. In other words, this command might help you to free up disk space.

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